1. In a 4- to 5-quart pan over high heat, bring 2 quarts water to a boil. Add the pasta, stir, and cook until tender to bite, 5 to 6 minutes. Drain, immerse in cold water until cool, about 3 minutes, and then drain again.
2. Meanwhile, tear chicken into shreds and place in a bowl. Add vinegar, fish sauce, ginger, cool noodles, and 2 tablespoons rau ram. Mix, and add more rau ram to taste. Mound salad onto plates and sprinkle equally with peanuts.